The present invention relates to a method and apparatus for detecting and sorting out articles improperly formed by a tool machine of the type having one relatively fixed machining element and a cooperating moveable machining element. Such machines include, among others, bolt trimming machines and thread forming machines as well as bolt forming machines which include both a trimming section and a thread forming section. In automatic bolt trimming machines and in bolt machines incorporating an automatic bolt trimming station, the blanks to be trimmed are periodically fed by suitable fingers to the bolt trimming station where a movable trimming die moves toward the holding die and during such movement engages the blank thus removing it from the fingers and inserting it in the holding die. During the last portion of the trimming die's movement toward the holding die the head of the bolt is shaped or cut to the desired shape, commonly hexagonal. At the end of the forward stroke the trimming die becomes relatively stationary and an ejection pin mounted within the holding die moves toward the trimming die to push the bolt into the channel within the trimming die to complete the cutting and shaping of the head and at the same time ejecting the same from the die. The ejection pin is operated by means of a lever and cam arrangement movement of which is integrated with the movement and, in particular, the completion of movement of the movable trimming die. At times, the trimming die becomes dull or pieces are broken out of the trimming die. When this occurs the ejection pin no longer has sufficient force to complete the trimming operation and eject the blank into the discharge channel within the trimming die. As a result the blank stays in the trimming die and upon the next stroke the blank hits the new product positioned in front of the holding die by the conveying fingers. As a result, various elements of the finger conveyor, the trimming die, or the holding die can be seriously damaged or destroyed.
One object of the present invention is to automatically detect blanks which have not been properly trimmed and ejected by monitoring the ejection pin which, under such circumstances, will not have made its full movement during the prescribed portion of the cycle. Upon detection of such an inaccurately trimmed product a portion of the machine, or all of the machine, is stopped automatically.
In automatic thread rolling machines, the blanks to be provided with thread are periodically fed to a pair of flat or cylindrical thread forming elements or dies, one of which is stationary and the other movable. The movable die is coupled to a rotating drive shaft which cyclically moves it past the stationary die to form a thread on the blank or work piece as it is rolled between the two dies. In such automatic thread rolling machines, the feeding of the blanks is coordinated with the movement of the movable die so that the blanks are inserted between the dies when the latter are at a predetermined position with respect to each other and the blanks are discharged at the end of the thread rolling cycle, after a predetermined movement of the movable die relative to the stationary die. Due to causes such as improper feeding of the blanks, the machine occasionally produces articles with a defective thread, for example, an overrolled thread or a thread with an improper geometry. Such defects in the thread on the finished articles are difficult to detect visually rendering the task of sorting the improperly thread rolled articles from correctly rolled ones, an expensive and time-consuming process since the finished products must be checked one by one.
One object of the present invention is to automatically detect articles rolled with a thread which does not meet the prescribed production requirements and to automatically separate those articles from ones with a correctly formed thread. Another object is to monitor the number of incorrectly formed articles and if the number exceeds a prescribed limit for a production run then to signal the operator, shut down the machine, or both.